The helicopter HUP-1 has been developed by the Piasecki company 1948. The first three test helicopters arrived to the test centre in spring 1949. The HUP-1 helicopter series consisted of 32 machines. Some of the helicopters were equipped with droppable hydro-acoustic stations. Parallel with the serial production the new modification HUP-2 was developed with more powerful engine R-975-42 and autopilot. The US NAVY has purchased 165 helicopters HUP-2, another 15 machines were transferred to French NAVY.